In the present invention an intrusion detection system comprises a detection element configured to detect an intrusion in a location, and to transmit an intrusion signal upon detection of the intrusion. The system further comprises a monitoring device configured to capture images of the location upon the detection of the intrusion, and to transmit image signals representing the captured images. A single transmission line is in electrical communication with the detection element and the monitoring device, wherein the transmission line is configured to carry both the intrusion signals and the image signals.